Turbine systems are widely utilized in fields such as power generation. For example, a conventional gas turbine system includes a compressor, a combustor, and a turbine. In a conventional gas turbine system, compressed air is provided from the compressor to the combustor. The air entering the combustor is mixed with fuel and combusted. Hot gases of combustion flow from the combustor to the turbine to drive the gas turbine system and generate power.
Many components of a turbine system require machining before installation in the turbine system. One example of such a component is a shroud block. Many such shroud blocks are located in the turbine section of a turbine system. For example, a plurality of shroud blocks may be disposed in an annular array radially outward of the rotor blades and axially between the nozzles in a turbine system, forming shrouds surrounding the rotor blades and nozzles. Typically, shrouds are provided in each stage of the turbine section of the turbine system. In, for example, a gas turbine system, the shrouds may partially define the radial outer boundary of the hot gas path flowing therethrough.
Shroud blocks typically define a variety of bore holes therein, which generally serve a variety of purposes. For example, retaining pin holes may be provided to accept retaining pins therein. The retaining pins may serve to position and retain the shroud blocks within the turbine section. Other bore holes, such as cooling holes, may be provided to accept cooling medium therein, to cool the shroud blocks and/or other components of the turbine system. Further, bore holes such as borescope holes and/or probe holes may be provided for inspection purposes. These various bore holes must be machined into the shroud blocks at precise locations and angles, and with small tolerances, in order for the shroud blocks to be positioned correctly and function properly within the turbine section.
Typically, the process for machining the required bore holes into a shroud block on location and/or during a system outage is inaccurate and time-consuming. For example, the locations of the bore holes in the shroud are many times approximated based on the locations of mating bore holes or other components in the turbine section. After approximating the locations of the mating bore holes, the bore holes may be machined by placing the shroud block on a flat, planer surface, such as on the platform of a drill-press, and machining the bore holes at the approximated locations on the shroud block. Because the shroud blocks include various radial outer surfaces, the placement of these outer surfaces on planer surfaces for machining may cause the bore holes to be machined at inaccurate angles. The combination of approximated location and inaccurate angle may result in bore holes that, for example, cannot be mounted properly in the turbine section and/or allow leakage from the shroud or into the shroud.
Further, the current inaccurate processes for machining the require bore holes may require the shroud blocks to be repeatedly machined to modify the bore holes until they perform adequately. This repeated machining for each shroud block is time-consuming and inefficient, and increases the time during which the turbine system is shut down, resulting in increased losses in the performance and revenue generated from the system.
Thus, an improved method and apparatus for machining a shroud block would be desired in the art. For example, a method and apparatus that allow for accurate and efficient machining of bore holes into shroud blocks would be advantageous.